This invention relates generally to the field of threaded closures having tamper-evident rings which separate to remain on the associated container as the cap element is manually unthreaded. and more particularly to an improved form thereof.
In my prior U.S. Pat. No. 3,829,912, there is disclosed a closure of this general type in which the tabs are of substantial cross section, whereby they are forced to function in the so-called xe2x80x9cfirst modexe2x80x9d, in which the tabs flex to only a small degree from relatively unstressed condition to engage a bead on the container neck and transmit an axially-directed force which results in rupturing of the frangible bridges which interconnect the tamper-indicating ring with the threaded cap portion of the device.
In many prior art constructions, it is known to form the tamper-indicating ring with a relatively thin upper portion which may radially expand during installation of the closure upon the container to permit the tabs to override the bead on the container, following which the tab returns to its original unstressed condition. A typical closure of this type is illustrated and described in my U.S. Pat. No. 5,992,661, granted Nov. 30, 1999. Such tabs still require substantial unthreading of the closure before they are brought into operative contact with the bead on the container neck, albeit such tabs do operate more quickly than older flexible type tabs which operate in the so-called xe2x80x9csecond modelxe2x80x9d, and require inversion, so that they reduce the effective diameter of the tamper-indicating ring to less than that of the outside diameter of the bead on the container neck.
Briefly stated, the invention contemplates the provision of an improved tamper-evident closure of the class described, in which the tab configuration has been further refined to provide substantially immediate transmission of axially directed forces from the flexible tabs to the frangible bridges interconnecting the tamper-indicating ring and the threaded cap element of the closure. This is accomplished by providing pivoted tabs operating solely in the first mode, in which the tabs are initially molded to lie in a relatively radially inward position, such that when the closure is installed, the radially-extending bead on the container neck will pivot the tabs through slightly greater than ninety degrees to be wedged within an annular recess formed between the inner cylindrical surface of the upper portion of the tamper-indicating ring, and the upper surface of the thicker lower portion of the tamper-indicating ring, to remain in this position with an inner upper edge of each tab disposed closely proximate to an undersurface of the bead on the container neck, when the closure is completed seated. Thus, when an unthreading action occurs, only a nominal degree of rotation is necessary to start the bridge breaking function. During this function, substantially no further pivoting action of the tabs takes place.